Abstract
BackgroundThis comparative study aimed to demonstrate the differences between swept source OCT (SS-OCT) (1310 nm) and spectral domain OCT (SD-OCT) (840 nm) for the identification and measurement of anterior chamber angle (ACA) structures.MethodsSixty seven eyes from 67 healthy subjects underwent ACA imaging at the nasal and temporal sides using SS-OCT and SD-OCT with different wavelength (Tomey, 1310 nm and RTvue, 840 nm). Images were evaluated for the ability to distinguish angle structures including the Schwalbe’s line (SL), the Schlemm’s canal (SC) and the scleral spur (SS). The length of trabecular meshwork (LTM), the angle-opening distance (AOD500 and AOD750) and the length of Schlemm’s canal (LSC) were also measured.ResultsThe nasal identification rate for SL, SC and SS were 91.04%/89.55%, 50.75%/40.30% and 100.0%/74.63% (SS-OCT/SD-OCT), respectively. The temporal identification rate for SL, SC and SS were 86.57%/91.04%, 68.66%/70.15% and 100.0%/65.67% (SS-OCT/SD-OCT), respectively. Differences between SS-OCT and SD-OCT were found in terms of the visualization of the SS. With respect to the measurements of angle, the evaluation of LTM at the nasal side, LSC at the temporal side and AOD500/750 at both sides showed significant difference between the two devices. However, there existed good correlation between the AOD500/750 measured by SS-OCT and SD-OCT (Spearman’s rank correlation coefficient > 0.8, p < 0.000).ConclusionsSS-OCT displayed a better performance in detecting deeper structures of the angle such as the SS. However, for discriminating structures lying in transparent or semi-transparent tissue such as the SL and the SC, the two devices showed good consistency. Although SS-OCT and SD-OCT demonstrated high correlation for angle measurement (AOD500/750), their agreement was poor.
Highlights
This comparative study aimed to demonstrate the differences between swept source OCT (SS-OCT) (1310 nm) and spectral domain OCT (SD-OCT) (840 nm) for the identification and measurement of anterior chamber angle (ACA) structures
Identification of angle structures scleral spur (SS)-OCT Using SS-OCT OCT, the SS, s line (SL), and s canal (SC) were identified in 67(100%)/67(100%), 61(91.04%)/58(86.57%), and 34(50.75%)/46(68.66%) of subjects at the nasal and temporal quadrants, respectively. (Table 1)
SD-OCT Using SD-OCT OCT, the SS, SL, and SC were identified in 50(74.63%)/44(65.67%), 60(89.55%)/61(91.04%), and 27(40.30%)/47(70.15%) of subjects at the nasal and temporal quadrants, respectively. (Table 1)
Summary
This comparative study aimed to demonstrate the differences between swept source OCT (SS-OCT) (1310 nm) and spectral domain OCT (SD-OCT) (840 nm) for the identification and measurement of anterior chamber angle (ACA) structures. Remaining the gold standard for the evaluation of ACA, the gonioscopy permits direct visualization of angle structures through microscopeaided eyes. The evaluation is relatively subjective and falls short of precision. The introduction of ultrasound biomicroscopy (UBM) and anterior segment optical coherence tomography (AS-OCT) paved the way for precise angle measurement. Compared to UBM, AS-OCT provides noncontact, in vivo imaging of ACA together with other benefits such as higher axial resolution and shorter acquisition time [1, 2]. The application of Fourier-domain OCT (FD-OCT) was expanded in the field of angle assessment with higher resolution and scanning speed in contrast to time-domain OCT (TD-OCT).
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